Re: [zfs-discuss] Re: Big JBOD: what would you do?

[Richard Elling]

Rich Teer wrote:

On Sat, 22 Jul 2006, Richard Elling wrote:


This one stretches the models a bit.  In one model, the MTTDL is


For us storage newbies, what is MTTDL?  I would guess Mean Time
To Data Loss, which presumably is some multiple of the drives'
MTBF (Mean Time Between Failures)?


Correct,
MTTDL = Mean Time To Data Loss
MTBF = Mean Time Between Failures
MTTR = Mean Time To Recover
MTBS = Mean Time Between Services (eg. repair action)
MTBSI = Mean Time Between Service Interruption

When we talk about retention, we worry about MTTDL.
When we talk about data availability, we worry about MTBSI.
When we talk about spares stocking or service intervals, MTBS.
Systems architecture, component selection, and configuration all
interact with each other.  It would be nice to have some really
good dependability benchmarks to apply, but that discipline is
still in its early stages.
 -- richard
___
zfs-discuss mailing list
zfs-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/zfs-discuss

Re: [zfs-discuss] Re: Big JBOD: what would you do?

[Richard Elling]

Thanks Rob, one comment below.

Rob Logan wrote:

perhaps these are good picks:

5 x (7+2)  1 hot spare  35 data disks  - best safety
5 x (8+1)  1 hot spare  40 data disks  - best space
9 x (4+1)  1 hot spare  36 data disks  - best speed
1 x (45+1) 0 hot spare  45 data disks  - max space


This one stretches the models a bit.  In one model, the MTTDL is
~1200 years and in a more detailed model, it is 6 years.  Most
people will be very unhappy with an MTTDL of 6 years.  To put
this in perspective, a 46-disk RAID-0 has an MTTDL of less than
2 years in all models.

I'd like to hear from the ZFS team how such a wide stripe would
be expected to perform :-)
 -- richard
___
zfs-discuss mailing list
zfs-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/zfs-discuss